1. Field of the Invention
The invention refers to a trestle being movable on a floor chassis comprising driveable caterpillars and having an approximately rectangular horizontal projection and serving the purpose of supporting the roof in underground cavities, in particular serving the purpose of securing the excavating edge when recovering pillars in coal mining, said trestle comprising a roof cap being supported against a base frame by hydraulically expandable props extending approximately vertically relative to stratification.
2. Description of the Prior Art
Such trestles are, as a rule, used in upright position one beside the other and serve the purpose to support the roof if the coal pillars remaining during excavation work shall be excavated. In such a case, the trestles shall be supported one against the other, on the one hand, and against the coal pillars, on the other hand, and shall again be removed out of the excavated material, so that they can again be used.